Modern communication networks are characterized by features such as high bandwidth/data-rate, complex communication protocols, various transmissions medium, and various access means. Fiber optic networks span much of the world's surface, acting as long-haul networks for carrying tremendous amounts of data between distant points on the globe. Cable and other wire-based networks supplement coverage provided by fiber optic networks, where fiber networks have not yet been installed, and are still used as part of local area networks (“LAN”), for carrying data between points relatively close to one another. In addition to wire-based networks, wireless networks such as cellular and other wireless networks (e.g. 2G, 3G, CDMA, WCDMA, WiFi, mobile TV, digital TV, etc.) are used to supplement coverage for various devices (e.g. cell phone, wireless IP phone, wireless internet appliance, etc.) not physically connected to a fixed network connection. Wireless networks may act as complete local loop networks and may provide a complete wireless solution, where a communication device in an area may transmit and receive data from another device entirely across the wireless network.
With the proliferation of communication networks and the world's growing reliance upon them, proper performance is crucial. High data rates and stable communication parameters at low power consumption levels are highly desirable for mobile communication devices. However, degradation of signal-to-noise ratio (“SNR”) as well as Bit energy to noise ratio (“Eb/No”) and interference ratios such as Carrier to-Interference (“C/I”) ratio occur to a signal carried along a transmission medium (e.g. coax, unshielded conductor, wave guide, open air or even optical fiber or RF over fiber). This degradation and interferences may occur in TDMA, CSMA, CDMA, EVDO, WCDMA, FDMA and WiFi networks respectively. Signal attenuation and its resulting SNR degradation may limit bandwidth over a transmission medium, especially when the medium is air or open space.
Radio Frequency (“RF”) based wireless communication systems ranging from cellular communication systems to satellite radio broadcasting systems are highly prevalent, and their use is consistently growing. Due to the unshielded nature of the transmission medium of wireless RF based communication systems, they are particularly prone to various phenomena, including interference signals or noise and fading signals, which tend to limit performance of such systems.
Thus, strong and stable signals are needed for the proper operation of a wireless communication device. In order to improve the power level of signals being transmitted over relatively long distances, and accordingly to augment the transmission distance and/or data rate, devices may utilize power amplifiers to boost transmission signal strength. In addition to the use of power amplifiers for the transmission of communication signals, receivers may use low noise amplifiers (“LNAs”) and variable gain amplifiers (“VGAs”) in order to boost and adjust the strength and/or amplitude of a received signal.
An additional problem with wireless RF based transmissions is that they may be characterized by a multipath channel between the transmitter antenna and the receiver antenna which introduces “fading” in the received signal power. The combination of attenuation, noise interference and “fading” is a substantial limitation for wireless network operators, mitigating their ability to provide high data-rate services such as Internet access and video phone services.
Some modern RF receivers may use various techniques and circuits implementing these techniques to compensate for phenomenon resulting from weak signal and interference. For example, the gain settings of the internal amplifiers may be adjusted based on the condition of the RF spectrum in which the receiver operates. Methods for adjusting the gain of internal amplifiers based on signal interference are well known. However, they do not take into account the many variations and permutations of interference that may occur in a wireless communication network.
There exists a need in the field of wireless communications for methods, circuits, devices and systems for enhancing communication signal reception by a wireless receiver.